Heat pump water heater exhausting/supply to ventilated crawl?
joenorm
| Posted in General Questions on
Would there be a compelling reason not to do this?
The area I have for my hot water heater is below my stairs, definitely don’t have the room area to not have supply and exhaust go to the exterior if I am to use a heat pump water heater.
Venting to an exterior wall is not a great option. But it would be easy to have the supply and exhaust go right through the floor and into a vented crawlspace?
Would there be a good reason not to do this?
Thanks
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Replies
If you have a vented crawl you would not want to do this.
If you have a conditioned crawl using the water heater to lower the temp of the crawl you risk making the walls of the crawl fall below the dew point that would allow mold to grow.
If you are in a hot dry climate no problem.
Walta
I can't see why you couldn't use the crawl space for the air inlet, but I would dump the exhaust outside. Make sure your heat pump water heater is rated for the expected outdoor air temperature, not all will run bellow 40F.
Why would you not dump exhaust into crawlspace?
A basement is air sealed, so the heat pump can remove humidity, that is not the case with a vented crawl space. Since it is connected to the outdoors, there is nothing limiting humidity, the cool exhaust in there could create moisture issues.
There might also not be enough air volume in there to supply the amount of heat the heat pump needs. These typically need a 750 ft3 in a basement, since a crawl space is colder it probably needs even more, that is a pretty large crawl space
The intake should not be a problem as it just supplies slightly tampered outdoor air to the unit.
You could consider sealing the crawlspace, drawing air from the crawl as akos suggested and exhausting outside as crawlspace exhaust only ventilation. Another consideration is just sticking the whole unit in the crawlspace if you have a large enough space in part of it.
Joe,
No idea if this applies to your situation, but our code doesn't seem to allow any air-intakes or exhausts in either ventilated attics or crawlspaces.
The air you vent into the crawlspace will be replaced by outdoor air. So which would you rather have in your house?
If it's cooling season, you'd rather have the vent air, it's cooler.
If it's heating season and the vent air is warmer than the outdoor air, you'd rather have the vent air.
If it's heating season and the vent air is cooler than the outdoor air, you'd rather have outdoor air.
Unless you live in a very mild climate most of the year you'd rather have the vent air go into your home.
What about keeping it all in the envelope, and ducting the discharge to another part of the house (or outside the understair area)? You might be able to install a vent in the kickplate of your stairway above?